Spieth, from Dallas, matched T.J. Vogel of Fort Lauderdale, Fla., and Anthony Paolucci of Dallas at 10-under 134 at TPC Rivers Bend.
It is hard to play safe out here and, if you do that, you are going to give yourself some tough putts and you will start aiming shots and not hitting fairways, said Spieth, playing in his first Junior PGA. Being aggressive has always been my game plan and yesterday I got away from that. I will not do that anymore this week.
Paolucci shot a 66, and Vogel had a 68.
I played a bogey-free round today, which I can not complain about, but it could have been better, said Vogel, who has only two bogeys over his first 36 holes. My ball-striking was definitely better of the tee yesterday and it has to be for the rest of the week for me to win this championship.
Danielle Frasier of Encinitas, Calif., shot a 72 for a one-stroke lead in the girls division at 4-under 140. Karen Chung of Livingston, N.J.; Sarah Brown of Phillipsburg, N.J.; and Erynne Lee of Silverdale, Wash., were tied for second after 71s.
I have to keep giving myself chances, but it all comes down to putting, Frasier said. I have to be more aggressive then I was today. I played it a bit too safe.